It is known that at present radio and television receivers are operated by remote control. For example, remote control may be used to select a program, to adjust the volume as well as to set the brightness and the color contrast in color television receivers. However, remote controls are also used in many other fields of industry, as, for example, in the steering of vehicles and model aircraft.
Various methods exist for transmitting the control information. One transmission possibility exists in transmitting signals at different frequencies and then performing different functions by the selection of different frequencies. A remote control circuit requires a device which transmits the information and a device which receives the information.